JP4322530B2 - Can pinhole inspection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pinhole inspection method for a can in which a defective can is detected by detecting a pinhole in a formed can and an abnormality in a pinhole inspection is detected in a process of manufacturing a can by forming an aluminum (alloy) thin plate or the like About.
[0002]
[Prior art]
A can filled with a beverage or the like is generally formed by deep drawing or drawing-squeezing a tin-plated steel sheet or an aluminum alloy thin plate. In order to facilitate this processing, since the plate thickness is as thin as possible, pinholes may be generated during processing. From the viewpoint of safety and reliability, it is necessary to reliably detect this pinhole efficiently and discriminate a defective can.
[0003]
The pinhole inspection device uses a method of irradiating the can with light from the outside, detecting the light leaking inside with a sensor facing the opening of the can, and determining the presence or absence of the pinhole based on the detected amount It has been. As shown in FIG. 5, the conventional pinhole inspection apparatus detects light leaking inside the can with a sensor 100. Then, the determination circuit 101 compares the output of the sensor 100 with a threshold value, and when the output of the sensor 100 is higher than the threshold value, outputs a control signal for processing the can as a defective can. Further, in order to prevent malfunction due to excessive light input of the sensor 100, the presence or absence of a can to be inspected is detected. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
JP-A-6-109661 (page 3-4, FIG. 2)
[0005]
[Problems to be solved by the invention]
However, in the pinhole inspection apparatus shown in FIG. 2 of Patent Document 1, a plurality of cans are held and rotated by a turret board, and light leaking into the cans is detected by a sensor held at a fixed position. ing. With this device's pinhole detector, the presence or absence of a pinhole is determined by the combined light of the can and light leaking from the sliding part between the can and the sensor when the can passes the light receiving surface of the sensor. Therefore, there is a problem that a can without a pinhole is identified as a defective can due to this light leakage. Further, since excessive light input to a sensor that causes an abnormality in pinhole inspection is prevented by detecting the presence or absence of a can, there is a problem that an abnormality due to a poor holding state of the can cannot be prevented.
[0006]
The present invention has been made in view of the above points, and its purpose is to control the light source that irradiates the can within the time span in which the opening surface of the can passes the light receiving surface of the sensor, and to turn it on and off. Measure the output of the sensor multiple times, and determine the presence or absence of a pinhole based on the combination of the measured value and the comparison result of the threshold value, thereby preventing the generation of an erroneous control signal due to light leakage etc. An object of the present invention is to provide a pin hole inspection method for cans that can detect defective cans. Another object of the present invention is to provide a can pinhole inspection method capable of detecting an inspection abnormality due to disturbance from the inspection environment and preventing malfunction.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 holds the can, rotates the can around the reference axis, and sets the inspection area of the sensor in which the opening of the can is held at a fixed position. A can pinhole inspection method for detecting light from a plurality of light sources irradiated to the can by the sensor and detecting a pinhole of the can when passing through the can, wherein the opening of the can is received by the sensor A step of controlling the light source to be in an ON, OFF, ON state while passing through a surface, an amount of light inside the can when the light source is ON, and the can when the light source is OFF a step of the internal light intensity, detected by the sensor, the step of measuring a plurality of measurement values measured in step, it is determined whether or exceeds a preset threshold value, and outputs the determination result, 3 Times of the measured value If the threshold is 3 times or less, it is determined that the inspected can has no pinhole. If the threshold is exceeded 2 times, it is determined that there is a pinhole. If the threshold is exceeded 3 times And a step of judging that the inspection is abnormal due to light leakage caused by the deterioration of the seal or the holding state of the can.
[0008]
According to a second aspect of the present invention, in the pinhole inspection method for the can according to the first aspect, the time ratio of ON and OFF of the light source is the time for the opening of the can to pass through the light receiving surface of the sensor. It is set according to and is variable.
[0009]
According to a third aspect of the present invention, in the can pinhole inspection method according to the first or second aspect, the light source comprises a light emitting diode, and a plurality of light sources are arranged at positions where the outer peripheral surface of the can is irradiated. It is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of the embodiment. In the figure, reference numeral 1 denotes a sensor, which uses a photomultiplier tube or the like. The can to be inspected is formed by deep drawing or drawing-ironing a thin metal plate, and the sensor 1 detects weak light or light that has passed through the inside of the can from the pinhole generated during this processing. Detect light leakage from the part. Then, the detected signal is amplified, a high frequency component is removed through a time constant circuit, and then output.
[0011]
Reference numeral 2 denotes a determination circuit that determines whether or not the output level of the sensor 1 exceeds a preset threshold value. The discrimination circuit 2 measures the output of the sensor 1 several times in accordance with the ON / OFF of the light source that irradiates the can within the time when the opening of the can to be inspected passes through the light receiving surface of the sensor 1, Make a comparison. Here, the light source is controlled to be in the ON, OFF, and ON states at the same time, and the output of the sensor 1 is measured at the center point of each state. The time width of ON and OFF is set according to the speed of the star wheel that holds and conveys the can.
[0012]
Reference numeral 3 denotes a storage circuit for storing a determination result obtained by comparing the measured value and the threshold value three times in the determination circuit 2, and reference numeral 4 denotes a control for reading the determination result from the storage circuit 3 and processing the can based on the determination result. The memory processing circuit outputs a signal. The memory processing circuit 4 determines that the inspected can has no pinhole and is “good” when the output level of the sensor 1 is three times or less of the threshold value among the three determination results read out. If the threshold is exceeded twice, there is a pinhole and it is determined as “defective”. If the threshold is exceeded three times, it is determined that the inspection is abnormal.
[0013]
Reference numeral 5 denotes a timing circuit for supplying a signal for determining the timing for comparing the output level of the sensor 1 and the threshold value in the discrimination circuit 2 and a timing signal for controlling the light source. Reference numeral 6 denotes an illumination control circuit that outputs a signal for controlling ON / OFF of the light source by a signal input from the timing circuit 5.
[0014]
The can is generally inspected by a pinhole inspection apparatus as shown in FIG. FIG. 3 is a schematic view of a longitudinal section of the pinhole inspection apparatus. The can 15 to be inspected is placed on the can fixing portions of the star wheels (conveying mechanisms) 19 and 20, and the bottom of the can is held by the spindle 17. The turret 13 and the star wheels 19 and 20 convey a plurality of cans while being rotated by the shaft 21. The star wheel 19, 20 rotates to convey the can 15, and the sensor 1 detects light inside the can 15 during the time when the opening of the can 15 passes through the light receiving surface of the sensor 1.
[0015]
The light source 16 is provided to irradiate the upper outer peripheral surface of the can 15, and the light source 18 is provided to irradiate the lower outer peripheral surface. The light sources 16 and 18 use a plurality of LEDs (Light Emitting Diodes) having a high response speed, and are configured so that the outer peripheral surface of the can 15 can be irradiated with light uniformly.
[0016]
In order to improve the light detection accuracy inside the can, the seal 14 attached to the turret 13 and the seal 12 attached to the support portion 11 of the sensor 1 prevent light from leaking from the sliding portion. FIG. 4 is a diagram showing an output signal of the sensor 1 attached to the pinhole inspection apparatus described above. The sensor 1 is highly sensitive, has dark current and residual noise, and outputs a signal 30 shown in FIG. 5A when there is no light input. Po is a threshold value for determining whether or not there is light from the pinhole.
[0017]
The time Ta-Tb is the time until the can 15 moves and enters the inspection area of the sensor 1, and Tb-Te is the time that the can 15 is within the inspection area of the sensor 1. Te−Tf is the time until the can 15 leaves the inspection area of the sensor 1 and the next can enters the inspection area. When the can 15 has a pinhole, the output signal of the sensor 1 has a waveform 31 shown in FIG.
[0018]
As shown in the figure, the output level of the sensor 1 exceeds the threshold Po at times Tb-Tc and Td-Te when the light sources 16 and 18 are ON. At the time Tc-Td when the light sources 16 and 18 are turned off, the output level becomes equal to or less than the threshold value Po. The determination circuit 2 measures the output level of the sensor 1 at times Tb-Tc, Tc-Td, and Td-Te at t1, t2, and t3, and compares it with the threshold value Po. When the output level exceeds the threshold Po, a signal “1” is output, and when the output level is equal to or lower than the threshold Po, a signal “0” is output.
[0019]
Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram showing a flow of processing of the pinhole inspection of the can. First, the illumination control circuit 6 turns on the light sources 16 and 18 for Tb-Tc time in which the can 15 is in the inspection region of the sensor 1, and turns it off at Tc. Further, Td is turned ON and Td-Te is turned ON (step S10). The sensor 1 detects, amplifies and outputs the light inside the can 15 in a state where the light sources 16 and 18 are controlled (step S11).
[0020]
The determination circuit 2 measures the output of the sensor 1 at times t1, t2, and t3 based on the timing signal supplied from the timing circuit 5 and compares it with the threshold value Po (step S12). When there is no pinhole in the can, the output of the sensor 1 has a waveform 30 shown in FIG. 4A, the comparison result becomes “0” at time t1, t2, and t3, and a signal “000” is output. When the can has a pinhole, the output of the sensor 1 has a waveform 31 shown in FIG. 4B, and a signal “101” is output.
[0021]
The storage circuit 3 stores the output signal of the determination circuit 2 (step S13). The memory processing circuit 4 reads the discrimination results at t1, t2, and t3 of the time Tb-Te stored in the memory circuit 3 (step S14), and discriminates the presence / absence of a pinhole based on the combination of the read signals. If there are two or more “0” s in the read signals, it is determined that there is no pinhole in the can (step S15: YES), and a control signal for processing as a good can is output (step S17).
[0022]
On the other hand, when “1” is two or more, it is determined that there is a pinhole in the can or that there is an abnormality in the inspection (step S15: NO), and the process proceeds to step S16. In step S16, if the signal read from the memory circuit 3 is “101”, it is determined that there is a pinhole in the can and not an inspection abnormality (step S16: NO), and the control signal to be processed as a defective can proceeds to step S19. Output.
[0023]
When there is a disturbance due to light leakage from the light detection portion, the holding state of the can 15 being defective, and the like, the inspection abnormal state is processed as follows in steps S15 and S16. The seal 12 prevents the light leakage from the sliding portion due to the rotation of the turret 13, but light leakage may occur depending on the deterioration of the seals 12 and 14 and the holding state of the can 15. The output waveform of the sensor 1 when light leakage occurs is as shown by the waveform 32 in FIG. In this case, even when the light sources 16 and 18 are OFF (Tc−Td), light exceeding the threshold Po leaks due to disturbance from the inspection environment, and the output of the determination circuit 2 becomes “111”.
[0024]
The memory processing circuit 4 reads this signal “111” from the memory circuit 3, and determines in step S15 that there is a pinhole or that there is a test abnormality. Further, in step S16, since the signal is “111”, it is determined that there is a disturbance such as light leakage and the inspection is abnormal (step S16: YES), and processing in the case of the inspection abnormality is performed (step S16: YES). Step S18).
[0025]
【The invention's effect】
As described above, according to the first aspect of the present invention, the light source that irradiates the can is controlled while the opening of the can passes through the inspection region of the sensor, and the light source is turned on and off. The light inside the can is measured multiple times, and the presence or absence of pinholes and pinhole inspection abnormalities are detected by the combination of the judgment results of whether the measured value exceeds the threshold value. It is possible to eliminate the influence and to inspect the pinhole with high accuracy, thereby obtaining the effect that the safety and production efficiency of the can can be improved.
[0026]
According to the second aspect of the present invention, since the optimal light source control and light detection timing can be set according to the speed at which the can of the pinhole inspection apparatus is transported, it can be adapted to the operational status of the pinhole inspection apparatus. It can deal with more flexibility and maintain high pinhole detection accuracy.
Further, according to the invention described in claim 3, since the LED having a high response speed is used as the light source, it is possible to stably control the light source even in an inspection in which the conveyance speed of the can is high. Reliability can be increased.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a pinhole detection unit according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a flow of pinhole detection processing.
FIG. 3 is a schematic longitudinal sectional view of a pinhole inspection apparatus.
FIG. 4 is a diagram illustrating sensor output waveforms and output level detection.
FIG. 5 is a diagram illustrating a configuration of a conventional pinhole detection unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sensor 2 Discriminating circuit 3 Memory circuit 4 Memory processing circuit 5 Timing circuit 6 Lighting control circuit

Claims (3)

Holding the can, rotating the can around a reference axis, and when the opening of the can passes through the inspection region of the sensor held at a fixed position, the light emitted to the can from a plurality of light sources is applied to the sensor. A can pinhole inspection method for detecting the pinhole of the can by detecting by
While the opening of the can passes through the light receiving surface of the sensor, the step of controlling the light source to ON, OFF, ON,
Detecting and measuring the amount of light inside the can with the light source turned on and the amount of light inside the can with the light source turned off by the sensor; and
Determining whether or not a plurality of measured values measured in the step exceeds a preset threshold value, and outputting a determination result;
If the measured value of 3 times is less than or equal to the threshold value 3 times, it is determined that the inspected can has no pinhole, and if it exceeds the threshold value 2 times, it is determined that there is a pinhole and 3 times If the threshold is exceeded, the step of judging an abnormality in the inspection due to light leakage caused by the deterioration of the seal or the holding state of the can;
A method for inspecting a pinhole of a can. 2. The pinhole inspection of a can according to claim 1, wherein the ON / OFF time ratio of the light source is set and variable according to a time during which the opening of the can passes the light receiving surface of the sensor. Method.   3. The can pinhole inspection method according to claim 1, wherein the light source includes a light emitting diode, and a plurality of the light sources are disposed at positions where the outer peripheral surface of the can is irradiated.

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